The synthesis of preferred polybenzimidazole based high performance fibers requires the selective condensation polymerization of 2,3,5,6-tetraminotoluene (“TAT”) with various substituted and unsubstituted aromatic diacids, such as 2,5-dihydroxyterephthalic acid (“DHTA”). The ratio of diacid to tetraamine should be as close to 1:1 as possible to achieve high enough molecular weight to produce fibers with good enough mechanical properties. In addition, safety concerns, especially with respect to sensitizing properties of some intermediates, should be addressed.
A need thus remains for a safe, efficient process for the production of suitable high-purity TAT-diacid monomer complexes that can be polymerized to a high molecular weight polymer material for producing high-performance fibers.